/**
 * Copyright (C) 2013 DaiKit.com - daikit-commons module (admin@daikit.com)
 *
 *         Project home : http://code.daikit.com/commons
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.daikit.commons.shared.utils;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;


/**
 * Utils for {@link Collection}
 *
 * @author tcaselli
 * @version $Revision$ Last modifier: $Author$ Last commit: $Date$
 */
public class DkCollectionUtils
{

	/**
	 * Construct a new {@link HashSet} from given objects.
	 *
	 * @param objects
	 * @return a {@link Set}
	 */
	public static final <T> Set<T> asSet(@SuppressWarnings("unchecked") final T... objects)
	{
		final Set<T> set = new HashSet<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				set.add(t);
			}
		}
		return set;
	}

	/**
	 * Construct a new {@link HashSet} from given {@link Collection} of objects.
	 *
	 * @param objects
	 * @return a {@link Set}
	 */
	public static final <T> Set<T> asSet(final Collection<T> objects)
	{
		final Set<T> set = new HashSet<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				set.add(t);
			}
		}
		return set;
	}

	/**
	 * Construct a new {@link HashSet} from given objects skipping null objects.
	 *
	 * @param objects
	 * @return a {@link Set}
	 */
	public static final <T> Set<T> asSetSkipNulls(@SuppressWarnings("unchecked") final T... objects)
	{
		final Set<T> set = new HashSet<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				if (t != null)
				{
					set.add(t);
				}
			}
		}
		return set;
	}

	/**
	 * Construct a new {@link HashSet} from given {@link Collection} of object skipping null objects.
	 *
	 * @param objects
	 * @return a {@link Set}
	 */
	public static final <T> Set<T> asSetSkipNulls(final Collection<T> objects)
	{
		final Set<T> set = new HashSet<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				if (t != null)
				{
					set.add(t);
				}
			}
		}
		return set;
	}

	/**
	 * Construct a new {@link ArrayList} from given objects
	 *
	 * @param objects
	 * @return a {@link List}
	 */
	public static final <T> List<T> asList(@SuppressWarnings("unchecked") final T... objects)
	{
		final List<T> list = new ArrayList<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				list.add(t);
			}
		}
		return list;
	}


	/**
	 * Construct a new {@link ArrayList} from given objects
	 *
	 * @param collections
	 * @return a {@link List}
	 */
	@SafeVarargs
	public static final <T> List<T> asList(final Collection<? extends T>... collections)
	{
		final List<T> list = new ArrayList<T>();
		if (collections != null)
		{
			for (final Collection<? extends T> collection : collections)
			{
				list.addAll(collection);
			}
		}
		return list;
	}

	/**
	 * Construct a new {@link ArrayList} from given {@link Collection} of objects
	 *
	 * @param objects
	 * @return a {@link List}
	 */
	public static final <T> List<T> asList(final Collection<T> objects)
	{
		final List<T> set = new ArrayList<T>();
		if (objects != null)
		{
			for (final T t : objects)
			{
				set.add(t);
			}
		}
		return set;
	}

	/**
	 * Construct a new {@link HashMap} from given array of objects
	 *
	 * @param objects
	 * @return an {@link HashMap}
	 */
	@SuppressWarnings("unchecked")
	public static final <K, V> Map<K, V> asMap(final Object... objects)
	{
		final Map<K, V> map = new HashMap<K, V>();
		K key = null;
		for (int i = 0; i < objects.length; i++)
		{
			if (i % 2 == 0)
			{
				key = (K) objects[i];
			}
			else
			{
				map.put(key, (V) objects[i]);
			}
		}
		return map;
	}

	/**
	 * Convert the source {@link Collection} of type S to target {@link List} of type T.
	 *
	 * @param objects
	 *           the source list of object to convert, values must be instances of S
	 * @param converter
	 *           the list converted, values are of type T
	 * @return the converted list
	 */
	public static final <S, T> List<T> convert(final Collection<S> objects, final Converter<S, T> converter)
	{
		final List<T> output = new ArrayList<T>();
		if (objects != null)
		{
			for (final S input : objects)
			{
				output.add(converter.convert(input));
			}
		}
		return output;
	}

	/**
	 * Converter for {@link #convert(Object)}
	 *
	 * @author tcaselli
	 * @version $Revision$ Last modifier: $Author$ Last commit: $Date$
	 * @param <S>
	 *           the source type
	 * @param <T>
	 *           the target type
	 */
	public static interface Converter<S, T>
	{
		/**
		 * Convert the source of type S to target type T.
		 *
		 * @param source
		 *           the source object to convert, which must be an instance of S
		 * @return the converted object, which must be an instance of T
		 */
		T convert(S source);
	}


}
